Morphological (light microscopy, electron microscopy) and biochemical (cytochemistry, biochemistry and molecular biology) approaches will be used in attacking diverse problems of cell biology. Intensive experience with a wide variety of normal and malignant cells should permit readier recognition of unique features that may become apparent in malignant cells. Cell transformation under the influence of oncogenic viruses, will be studied with special emphases on (1) cell surface glycoproteins and their possible role in the control of intracellular events, and (2) sites of synthesis of viral nucleic acid, protein and membrane components. Aspects of cell function to be studied, under physiological and pathological conditions, include: (1) dynamic interrelations of plasma membrane, Golgi apparatus, endoplasmic reticulum, and lysosomes; (2) formation and turnover of plasma membrane constituents, particularly the carbohydrate moieties of glycoproteins in normal and transformed cultured cells; (3) the special activities of the endoplasmatic reticulum region that we have named GERL; (4) the functional and structural polarity of the Golgi apparatus; (5) the synthesis, storage and degradation of lipid in the rat, hamster and other mammals.